For some plants species, silicon (Si) is absorbed from the soil in large amounts, which are greater than those of essential macronutrients, such as potassium, nitrogen and phosphorus. Silicon benefits plants by increasing their yields. It improves the physical properties of soil and the resistance of plants to disease and pests and increases the tolerance of plants to toxic elements, such as iron and manganese.
Much of the soil is comprised of silicon in different forms. For example, 40-70% of the clay soils contain silica (SiO2), while 90-98% of the sandy soils contain silica. Additionally, silicon may be in the form of a silicate, a salt or ester derived from silicic acid. However, silicate is not in a form of silicon that can be delivered to plants. Plants assimilate silicon as monosilicic acids (H4SiO4). Plants can adsorb from 70 to 700 kg of silicon/ha of soil. Plants transform much of the silicon into epidemical tissue.
Silicon has been shown to be vital in the growth of rice and sugarcane. Silicon is necessary for healthy and productive development of the rice plant. It reduces the severity of diseases in rice such as blast, brown spot, sheath blight, stem rot, and leaf scald. Seebold et al., Plant Disease, 871-76 (August 2000) Rice absorbs large amounts of silicon from the soil. For example a rice crop that produces a total grain yield of 5 tons/ha typically removes from 230-470 kg Si/ha (500-1000 kg SiO2/ha) from the soil. Thus even in soils that are initially able to provide sufficient silicon to the rice plants, as time passes the rice depletes the amount of silicon in the soil and supplemental silicon sources are needed.
Sugarcane is another agricultural product which requires a lot of silicon. Silicon prevents freckling in sugarcane. G. J. Gascho, Soil & Crop Soc'y Fla. Proc., 36: 188-191 (November 1976) Silicon is present in considerable quantities in the sugarcane plant. Silicon absorption is particularly high in the green leaves during the first six months of growth, after which it remains fairly constant. N. Rozeff, Sugar J., p. 20 (January 1992)
Many soils, including sandy flatwood soils, contain low levels of available silica and are very acidic. As plants assimilate the available silica from the soil into their tissue, the amount of available silica is depleted. The silicon deficiency in the soil has lead farmers to use different materials to increase the levels of available silicon in the soil.
Lime (CaO) is often added to acidic soil acidic to ensure that the soil is at the proper pH to allow for efficient uptake of nutrients, such as phosphorus, potassium, and nitrogen, and to prevent the delivery of toxic levels of substances, such as manganese and aluminum.
Reclime® contains calcium (26-28%), magnesium (6-8%), calcium carbonate equivalent (90-100%), soluble silicon (>10 lbs/ton). It is designed to provide soluble silicon and control the pH of the soil, like lime. Reclime® contains MgSiO3, which is very soluble in water. Therefore, the silicon from MgSiO3 is delivered quickly to the plant. However, Reclime® also contains aluminum and iron, which bind with the silica and reduce the amount of available silica. Thus, Reclime® is unable to provide sufficient silicon to the plants for a sustained period of time without frequent applications.
U.S. Pat. Nos. 5,743,934 and 5,997,599 to Wommack et al. disclose water disintegratable pellets formed from cement kiln dust and a water soluble binder. Additionally primary plant nutrients, secondary plant nutrients (magnesium, sulfur, and/or calcium), and or micronutrients (iron, copper, etc) may be present in the pellets. At least 15% of the resulting pellet is from a calcium source, such as kiln dust, lime, limestone, or gypsum. This results in a pellet with a small amount of silica. The small quantity of silica in the pellet does not provide enough silica for efficient uptake of nutrients by plants. Thus, large amounts of the pellets must be applied to the soil to provide a sufficient amount of silica for the plants.
Dolomite, formed of calcium magnesium carbonate (CaMg(CO3)2), is used in agriculture, residential or commercial lawns and golf courses. It is applied to lawns to increase the pH of the soil, while delivering the nutrients, calcium and magnesium, to the soil. However, Dolomite does not provide any silica to the soil. Thus a separate silica source must be administered in addition to Dolomite, which increases the cost of the treatment for the soil.
Calcium silicate (CaSiO2) (CS) slag is obtained as a bi-product from the mining of metals. It has been used for agricultural purposes to deliver silicon to plants. In mild acidic conditions, silicon becomes soluble so that it can travel through the soil to the roots of the plants. Studies have demonstrated that during the early growth stage for rice plants, the application of CS slag increases the soil's pH and calcium concentration. However, CS slag does not provide magnesium to the soil. Thus a separate source for magnesium must be added to the soil, thereby increasing the cost for the soil treatment.
It is therefore an object of the invention to provide a more cost-effective soil enhancer for use in agriculture, residential or commercial lawns and golf courses.
A further object of the invention is to provide a soil enhancer that delivers nutrients to plants for a prolonged period of time.